E911

Enhanced 911, E-911 or E911 is a system used in North America that links emergency callers with the appropriate public resources. Three-digit emergency telephone numbers originated in the United Kingdom in 1937 and have spread to continents and countries around the globe. Other easy dial codes, including the 112 number adopted by the European Union in 1991, have been deployed to provide free-of-charge emergency calls.

In North America, where 9-1-1 was chosen as the easy access code, the system tries to automatically associate a location with the origin of the call. This location may be a physical address or other geographic reference information such as X/Y map coordinates. The caller's telephone number is used in numerous manners to track a location that can be used to dispatch police, fire, emergency medical and other response resources. Automatic location of the emergency makes it faster to locate the required resources during fires, break-ins, kidnappings, and other events where communicating one's location is difficult or impossible.

In North America the incoming 9-1-1 call is normally answered at the Public Safety Answering Point (PSAP) of the governmental agency that has jurisdiction over the caller's location (see #Location below). When the 9-1-1 call arrives at the appropriate PSAP, it is answered by a specially trained official known as a Telecommunicator. In some jurisdictions the Telecommunicator is also the dispatcher of public safety response resources. When a landline call arrives at the PSAP, special computer software uses the telephone number to retrieve and display the location of the caller in near real-time upon arrival of the call.

The system only works in North America if the emergency telephone number 911 is called. Calls made to other telephone numbers, even though they may be listed as an emergency telephone number, may not enable this feature. Outside Canada, Mexico, and the United States this type of facility is often called caller location, though its implementation is dependent on how the telephone network processes emergency calls.

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